<!-- 渐变色：linear-gradient（方向（to right、起始颜色、结束颜色-->
<!-- <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            background-image: linear-gradient(to right, #fff, #000);
        }
    </style>
</head>
<body>
    
</body>
</html>
 -->
<!-- 平滑过渡 ：transition 动画颜色过渡平滑 -->
<!-- <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            transition: background-color 0.3s;
        }
    </style>
</head>
<body>
    
</body>
</html> -->

<!-- 图片垂直居中：line-height、绝对定位、flex弹性盒子、table-cell -->
<!-- <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            display: flex;
            /* 垂直方向 */
            justify-content: space-around;
            /* 水平方向 */
            align-items: center;
        }
    </style>
</head>
<body>
    
</body>
</html> -->
<!-- display: table-cell;
vertical-align: middle; -->
<!-- <!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            display: table-cell;
            vertical-align: middle;
        }
    </style>
</head>

<body>

</body>

</html> -->